Tire Size/Traction

[2 GTOs]

Assuming the same brand in 2 different sizes, 245/40/18 and 275/35/18, is the difference in traction on the street very noticeable? Trying to figure out if the performance increase is worth buying rims and fender rolling, or if this really is more of an appearance mod for most people.

No track use so I am not looking to pick up .001, etc

Thanks

[torridgto79]

265/35/18 will fit on the stock 18" i hear

[DAFFYDRUNK]

In straight line traction, my opinion is that it's mostly an appearance mod. While the foot print of a fatter tire is indeed wider, the skinnier tire will have a longer foot print assuming the same tire pressure. Assuming the fatter tire is spec'd to have a similar diameter, the skinnier tire will also have more sidewall ratio to flex under load.

The second thing worth considering is wider tires tend to feel more sloppy and tend to wander more, especially in the front. Say you could go from 245 in the front to 275s... Sure you will corner better but the car will wanna wonder more when it hits ruts and grooves. I did exactly that on my old TA. Went from 245/50-16s to 275/40-17s and it was indeed sloppier although it did grip better.

Third thing to consider is rolling resistance. Larger tires have more rolling resistance. Gas mileage will go down a little. Another thing I noticed on my TA, when the battery died and I had to push the thing out to the street. It was a little harder to push the thing around. Rolling resistance could even play a small part is acceleration once you're past the point where the car could break traction?

In the end though I'd still go as wide as realistically possible. I'm not gonna cut or roll the fenders to do it though. I feel that it's just asking for paint issues down the road and it's best not to upset the factory paint around the wheels if you can help it.

[2 GTOs]

Thanks, I was planing to leave 245 in the front and maybe go wider in the rear only.

[cybernco]

I installed the Pedders Drag Strip II package that includes 5/16" taller rear springs, installed BMR Sub-Frame Connectors, installed a 1-Piece Aluminum drive shaft and then mounted BFGoodrich 275/40/17 sport summer tires. My traction is greatly improved however the sidewalls on the tires don't flex as good as the old 15" rimmed tires. If you are making a lot of rear wheel power then I'd recommend going directly to 15" rims all the way around to start. Yeah, you'll have to roll or cut the fenders but you'll end up with the best real world traction for hard launches.

[Jim346]

In straight line traction, my opinion is that it's mostly an appearance mod. While the foot print of a fatter tire is indeed wider, the skinnier tire will have a longer foot print assuming the same tire pressure. Assuming the fatter tire is spec'd to have a similar diameter, the skinnier tire will also have more sidewall ratio to flex under load.


Skinnier tire with longer foot print is just crazy talk if the diameter is the same. Same with the skinny tire having more sidewall when it has the same diameter. You aren't making any sense at all.

Anyway, I went from the stock 235-40-18 to a 245-40-18 on the front and a 275-35-18 on a 9.5" wide wheel on the rear. Straight line traction and grip in the turns was definitely improved.

[cybernco]

Skinnier tire with longer foot print is just crazy talk if the diameter is the same. Same with the skinny tire having more sidewall when it has the same diameter. You aren't making any sense at all.

Anyway, I went from the stock 235-40-18 to a 245-40-18 on the front and a 275-35-18 on a 9.5" wide wheel on the rear. Straight line traction and grip in the turns was definitely improved.

What about the benefit from additional sidewall flex in a tire thats the same diameter and width? This is in reference to converting from a 17" rim to a 15" rim strictly to gain additional sidewall height.

[nadthomas]

cybernco the original poster asked about "street use only", not track use. I'm not saying there isn't benefit for 15" wheels and tall sidewalls for the track, but that wasn't the original question.

[2 GTOs]

I take it from some of the posts that going from a 245/40/18 to a 275/35/18 does make a noticable different in spirited street driving then.

[Jim346]

What about the benefit from additional sidewall flex in a tire thats the same diameter and width? This is in reference to converting from a 17" rim to a 15" rim strictly to gain additional sidewall height.

He's comparing different widths for the same diameter tire on an 18" wheel, so I don't know why you're even talking about 15s and 17s.

[cybernco]

Yeah, I guess I was high-jacking the thread for my own advice. Sorry guys.

[DAFFYDRUNK]

Skinnier tire with longer foot print is just crazy talk if the diameter is the same. Same with the skinny tire having more sidewall when it has the same diameter. You aren't making any sense at all.

I wouldn't say crazy talk.
I'm thinking lbs per sq inch. Contact patch. Sure you may get more traction from the extra width, but since there is more width there is less pressure per sq inch to flatten out the face of the tire as the weight of the car is put on it. To visualize what I'm saying you could take a 245 and a 275 and put 30 lbs of pressure in each. Then mount each on your car. Put ink all over the tread and set them down on a large piece of paper. Jack the car back up then measure the area of ink for each one. The 275 will be wider but the skinnier 245 will sag more and have a longer contact patch. Between the 2, there probably won't be a significant difference in how much tire tread is actually touching the ground.

As for the side wall thing. I have a 245/45-17 right now. If I go fatter I could get a 275 40-17. If you notice in my posts I said the word "ratio", and I dunno if it would make a difference or not. I would think that it does for the same reason I argue that the contact patch on a tire isn't all that difference between a 245 and 275 tire once it has the weight of the car on it.

[SHS]

I respectively don't agree with you. Why does the Corvette have wider wheels and tires if contact patch doesn't matter?

Your paper test doesn't take into account the spinning characteristics of each tire. Also, the volume of air to produce 30 psi will be different for each wheel/tire combo BUT if the gauge says 30 psi it is 30 psi. The pressure per inch will be 30 psi no matter the wheel/tire combo.

To the original poster, a lot of people upsize for a reason. But, you could just find a stickier tire and getter much better traction. The stock tires BLOW. I am upsizing functionally. I can't wait.

The tax gods have been good to me this year. You know, I am liking all the tax cuts this administration has done. I am getting a PHAT check this year.

[Jim346]

I wouldn't say crazy talk.


Yes, crazy talk.

[cybernco]

I respectively don't agree with you. Why does the Corvette have wider wheels and tires if contact patch doesn't matter?

Your paper test doesn't take into account the spinning characteristics of each tire. Also, the volume of air to produce 30 psi will be different for each wheel/tire combo BUT if the gauge says 30 psi it is 30 psi. The pressure per inch will be 30 psi no matter the wheel/tire combo.

To the original poster, a lot of people upsize for a reason. But, you could just find a stickier tire and getter much better traction. The stock tires BLOW. I am upsizing functionally. I can't wait.

The tax gods have been good to me this year. You know, I am liking all the tax cuts this administration has done. I am getting a PHAT check this year.

I believe that he's referring to the Lbs per sq inch that is made between the tire tread and the road surface, not the PSI of the air inside the tire. He's right though, on a slick surface the wider tire doesn't have as much traction. I lived in the Midwest for 40 years and Winter driving with wide tires isn't new to me. However, when the road surface is warm & dry, the PSI to road contact isn't as important as putting a larger surface of that sticky tire down to the road. Does that make sense?

[SHS]

Okay, I see what he is saying. Your spreading the vehicles weight over more surface area. Then he should just get a stickier tire.

[Jim346]

All racecars and exotics will come with skinny tires from now on, you heard it here.

[Mike-Omologato-G.]

After modding the car from 345 rwhp to 430 rwhp, I have issues with traction, no doubt, lol. I have stock 17"s with Nitto EP555 255/45/17. They are about done, but don't even hold 1st gear at all, nor 2nd gear above 4000 rpm.

I have 2 choices:

1) Buy 4 new wheels and 4 new tires/roll fenders = $$
2) Buy 2 new rear tires, and see what fits and grips on the stock 17.

Please advise, since this thread is active.

[purplenurple]

After modding the car from 345 rwhp to 430 rwhp, I have issues with traction, no doubt, lol. I have stock 17"s with Nitto EP555 255/45/17. They are about done, but don't even hold 1st gear at all, nor 2nd gear above 4000 rpm.

I have 2 choices:

1) Buy 4 new wheels and 4 new tires/roll fenders = $$
2) Buy 2 new rear tires, and see what fits and grips on the stock 17.

Please advise, since this thread is active.

Do you care about looks? If not, then just get some KDW2 255s for the stock 17s. If you want better looks with better traction, I would get 18in staggered Thruxtons. Im not a fan of AM 18s, but the thruxtons go nicely with the CGM. Maybe you could try one of the new TSW wheels (Jarama, Indy 500)

[MVDCGTO]

Assuming the same brand in 2 different sizes, 245/40/18 and 275/35/18, is the difference in traction on the street very noticeable? Trying to figure out if the performance increase is worth buying rims and fender rolling, or if this really is more of an appearance mod for most people.

No track use so I am not looking to pick up .001, etc

Thanks

I was curious as well so I did a personal test. I bought my staggered setup mainly for looks but was curious if the 275's out back really made that much of a difference. I took the rears off and swapped the fronts to the rear (245/40/18) and put my stockers on the front. The car spun tire MUCH easier. I put everything back and tried it again and yeah it spun just not nearly as freely. So no matter what some here have to say wider is better for traction, may cause understeer with staggered setups but for straight line go wide.

[Jim346]

After modding the car from 345 rwhp to 430 rwhp, I have issues with traction, no doubt, lol. I have stock 17"s with Nitto EP555 255/45/17. They are about done, but don't even hold 1st gear at all, nor 2nd gear above 4000 rpm.

I have 2 choices:

1) Buy 4 new wheels and 4 new tires/roll fenders = $$
2) Buy 2 new rear tires, and see what fits and grips on the stock 17.

Please advise, since this thread is active.

Get a DR on the back if you don't want to spend the money for wider wheels.

[TXRaider]

Just M2c, but I felt like the addition of 275 to the rear, even your wheel spin won't improve too much, the car tracks more stable and straightens up better. For instance, with the 275's on the wheel spin is less prone to walking the back end around than with the stock 235 (for the 18's). Not very versed here on this matter, but would that be a by product of the staggered set up - better inherent stability? (at the cost of a little more under steer)

[cybernco]

After modding the car from 345 rwhp to 430 rwhp, I have issues with traction, no doubt, lol. I have stock 17"s with Nitto EP555 255/45/17. They are about done, but don't even hold 1st gear at all, nor 2nd gear above 4000 rpm.

I have 2 choices:

1) Buy 4 new wheels and 4 new tires/roll fenders = $$
2) Buy 2 new rear tires, and see what fits and grips on the stock 17.

Please advise, since this thread is active.

If you want to use the stock 17's with street only tires then I'd go with 275/40/17's. Maybe the Good Year Eagle F1 All Season tires? Either way they'll fit if you buy 2 each Pedders PN: 2589 rear springs that will raise the rear 5/16" and then roll or cut the lip of the rear fender. The springs go for $280 a pair and it'll cost about $100 to have the fender rolled. But that beats the price of 4 new rims and 4 new tires.

[Mike-Omologato-G.]

Yes it does beat the price of 4+4 purchase. I kinda put rolling the fenders as a benchmark for getting wider wheels, though.

Those DR's would have to get 10,000 miles on a DD. Possible ? I was thinkibng drag bags + DR if they last that long, and specifically, if they can handle the Monsoon Season.

[Lothar]

Look into the Dunlop SP Sport Maxx. They're very sticky and good in the rain. I got a little over 20,000 miles on my DD.

[Jim346]

Yes it does beat the price of 4+4 purchase. I kinda put rolling the fenders as a benchmark for getting wider wheels, though.

Those DR's would have to get 10,000 miles on a DD. Possible ? I was thinkibng drag bags + DR if they last that long, and specifically, if they can handle the Monsoon Season.

Not a good idea. You can go 10k miles if it's a lot of highway and you don't go to the track all that much...but those last 5k miles would be pure hell in the rain. They're great in the rain at first, but awful once they're half worn. On a nitto dr, the channels on the shoulder are about twice as deep as the ones in the center of the tire. Once they're a little worn, you're left with a solid patch of rubber about 4 or 5 inches wide in the center.

[Mike-Omologato-G.]

On a nitto dr, the channels on the shoulder are about twice as deep as the ones in the center of the tire. Once they're a little worn, you're left with a solid patch of rubber about 4 or 5 inches wide in the center.


Is that good or bad ? Wet weather traction is a MUST here in Houston. Any other advisers ?

The tire must handle 430 rwhp, and be good in the rain, and last at least 10,000 miles. My Nittos EP555 have lasted 17,000 miles, and are not good anymore, unless it is Hot pavement and dry.

[Jim346]

Is that good or bad ? Wet weather traction is a MUST here in Houston. Any other advisers ?


In the rain that would be real bad.

[FraggerCrue]

Is that good or bad ? Wet weather traction is a MUST here in Houston. Any other advisers ?

The tire must handle 430 rwhp, and be good in the rain, and last at least 10,000 miles. My Nittos EP555 have lasted 17,000 miles, and are not good anymore, unless it is Hot pavement and dry.

Leave the DRs alone. Jax is much like Houston, too much rain for DRs on the street. Go to tirerack, look up tire by size (275/45-17), then select 'performance category', read desciptions and select accordingly.

Nothing will handle 430rwhp on the street, not even M/T DRs. Been there, done that.